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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Astronomy and Space Sciences
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The Korean Space Science Society
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Volume & Issues
Volume 20, Issue 4 - Dec 2003
Volume 20, Issue 3 - Sep 2003
Volume 20, Issue 2 - Jun 2003
Volume 20, Issue 1 - Mar 2003
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RELATIONSHIP BETWEEN GEOMAGNETIC STORMS AND RELATIVISTIC ELECTRON EVENTS
Kim, Hee-Jeong ; Lee, Dae-Young ;
Journal of Astronomy and Space Sciences, volume 20, issue 2, 2003, Pages 95~100
DOI : 10.5140/JASS.2003.20.2.095
This paper is for the investigation of the relationship between the geomagnetic disturbances and the relativistic electron events occurring at geosynchronous orbit. We have analyzed the electron fluxes of E > 2 MeV measured by GOES 10 satellite and the hourly Dst index for the period of April, 1999 to December, 2002. With the rigorous definition of the relativistic event, total 34 events were identified during the time period. Our statistical study showed that more than 50% of the total events occurred associated with weak (or sometimes virtually no) magnetic storms. And only ~ 20% of the events took place accompanied by a strong magnetic storm of
< -100 nT. This result suggests that large geomagnetic storms may not be crucial for the occurrence of a relativistic event at geosynchronous orbit. We also found that there is no clear correlation between the maximum electron flux of an event and the associated minimum of Dst. Therefore any study on the physical mechanism (s) accounting for the relativistic events should take it into account that strong magnetic storms may not be necessarily required for the occurrence of a relativistic electron event at geosynchronous orbit.
RECURRENT PATTERNS IN DST TIME SERIES
Kim, Hee-Jeong ; Lee, Dae-Young ; Choe, Won-Gyu ;
Journal of Astronomy and Space Sciences, volume 20, issue 2, 2003, Pages 101~108
DOI : 10.5140/JASS.2003.20.2.101
This study reports one approach for the classification of magnetic storms into recurrent patterns. A storm event is defined as a local minimum of Dst index. The analysis of Dst index for the period of year 1957 through year 2000 has demonstrated that a large portion of the storm events can be classified into a set of recurrent patterns. In our approach, the classification is performed by seeking a categorization that minimizes thermodynamic free energy which is defined as the sum of classification errors and entropy. The error is calculated as the squared sum of the value differences between events. The classification depends on the noise parameter T that represents the strength of the intrinsic error in the observation and classification process. The classification results would be applicable in space weather forecasting.
THE RELATIONSHIP BETWEEN PARTICLE INJECTION RATE OBSERVED AT GEOSYNCHRONOUS ORBIT AND DST INDEX DURING GEOMAGNETIC STORMS
Journal of Astronomy and Space Sciences, volume 20, issue 2, 2003, Pages 109~122
DOI : 10.5140/JASS.2003.20.2.109
To examine the causal relationship between geomagnetic storm and substorm, we investigate the correlation between dispersionless particle injection rate of proton flux observed from geosynchronous satellites, which is known to be a typical indicator of the substorm expansion activity, and Dst index during magnetic storms. We utilize geomagnetic storms occurred during the period of 1996 ~ 2000 and categorize them into three classes in terms of the minimum value of the Dst index (
); intense (
), and small (
) -30nT)storms. We use the proton flux of the energy range from 50 keV to 670 keV, the major constituents of the ring current particles, observed from the LANL geosynchronous satellites located within the local time sector from 18:00 MLT to 04:00 MLT. We also examine the flux ratio (
) to estimate particle energy injection rate into the inner magnetosphere, with
being the flux levels during quiet and onset levels, respectively. The total energy injection rate into the inner magnetosphere can not be estimated from particle measurements by one or two satellites. However, the total energy injection rate should be at least proportional to the flux ratio and the injection frequency. Thus we propose a quantity, “total energy injection parameter (TEIP)”, defined by the product of the flux ratio and the injection frequency as an indicator of the injected energy into the inner magnetosphere. To investigate the phase dependence of the substorm contribution to the development of magnetic storm, we examine the correlations during the two intervals, main and recovery phase of storm separately. Several interesting tendencies are noted particularly during the main phase of storm. First, the average particle injection frequency tends to increase with the storm size with the correlation coefficient being 0.83. Second, the flux ratio (
) tends to be higher during large storms. The correlation coefficient between
and the flux ratio is generally high, for example, 0.74 for the 75~113 keV energy channel. Third, it is also worth mentioning that there is a high correlation between the TEIP and
with the highest coefficient (0.80) being recorded for the energy channel of 75~113 keV, the typical particle energies of the ring current belt. Fourth, the particle injection during the recovery phase tends to make the storms longer. It is particularly the case for intense storms. These characteristics observed during the main phase of the magnetic storm indicate that substorm expansion activity is closely associated with the development of mangetic storm.
PHOTOMETRIC SOLUTIONS AND SPOT MODEL OF THE CONTACT BINARY AB ANDROMEDAE
Journal of Astronomy and Space Sciences, volume 20, issue 2, 2003, Pages 123~132
DOI : 10.5140/JASS.2003.20.2.123
We performed CCD photometric observations of the W-type contact binary AB And for 10 nights from November 1995 to December 1999 using the 61-cm reflector and BVR filters at Sobaeksan Optical Astronomy Observatory. From our observations, the seasonal light curves of AB And for 1995, 1996 and 1999 were completed and 8 new times of minimum light were determined. Newly obtained light curves show that strong light variations occurred in AB And during the past five years. We adopted the 1996 light curves as reference ones and obtained the photometric solutions of them with contact mode in the Wilson-Devinney binary code. Assuming such light variations were produced by the existence of a star spot (or star spots) in the analysis, we derived the system parameters and analyzed the 1995 and 1999 light curves by adjusting only the spot parameters. As the results, we interpreted that those light variations are produced by the simultaneous existence of a hot spot and a cool spot on the secondary. We could infer that the hot spot on the secondary is produced due to mass exchange between the components suggested by Lee (1999).
SMALL MASS RATIO CONTACT BINARY
Journal of Astronomy and Space Sciences, volume 20, issue 2, 2003, Pages 133~142
DOI : 10.5140/JASS.2003.20.2.133
The contact binary system has been classified in five different types according to their physical properties. We suggest that extremely small mass ratio contact binary systems(q＜0.2) could be classified as a new type of contact binaries in addition to the classification. According to the Svechnikov & Kuznetsova (1990)`s catalogue, the spectral types of primary components of newly classified contact binaries are distributed at A type, and also the distribution of their various physical characteristics is laid at the center region dividing the early-type contact binaries from late-type contact binaries.
A CONSTRUCTION OF A SEMI-AUTOMATIC TELESCOPE FOR ECLIPSE TIMING OBSERVATIONS OF ECLIPSING BINARY STARS
Journal of Astronomy and Space Sciences, volume 20, issue 2, 2003, Pages 143~152
DOI : 10.5140/JASS.2003.20.2.143
We constructed the photometric observation system with a small semi-automatic telescope for the systematic observations of eclipse timings of eclipsing binary stars. The system is consisted of a Paramount GT-1100s mount system, a Celestron 14 optical system, and a SBIG ST-8 camera. We developed the OBSTOOL S/W which controls the telescope and the CCD camera using the COM(Component Object Model) supported by the softwares, The Sky and MaximDL. The system performs photometric observations of a variable, comparison and check stars by moving the telescope to the chosen star separately in a similar way such as the method of photoelectric observation. We wrote pert scripts which enable a data handling pipeline for the obtained data to be classified by each of date, object and filter. And thus the images are easily preprocessed using the IRAF S/W package. Eclipse light curves of some eclipsing binary stars observed with this system are presented.
DEVELOPMENT OF TRACKING AND OBSERVING SYSTEM FOR MAN-MADE SPACE OBJECTS
Journal of Astronomy and Space Sciences, volume 20, issue 2, 2003, Pages 153~162
DOI : 10.5140/JASS.2003.20.2.153
Recently, we have reconstructed LX-200 12inch telescope system for tracking and observing man-made space object. Motor, motor driver and motion controller were up-graded for getting faster respond characteristic and active control available. Also, command signal was offered to the PID controller into motor driver as computed real orbiting information of objects using PC, and it`s control period of command signal was reduced to the 20ms. As the result, slew speed of the mount system was in proved up to
and respond speed of the system was faster than that of commercial system. Also, flipping state of image observed could be minimized by the up-graded system.